Further development and application of the ReOs isotope system in crustal geochronology

地质年代学是利用地球物质(岩石、矿物、矿石)中不稳定同位素的放射性衰变来确定绝对地质时间的科学。地球年代学要求将物理、化学和数学与地球科学相结合，以了解在46亿年的历史中塑造我们星球的过程。Re-Os(187Re-187Os)放射性同位素系统是地球科学中最后实施的系统之一，主要是由于分析困难。虽然Re-Os系统只适用于选定的地壳岩石和矿物，但这些岩石和矿物恰好是更常用的放射性测年系统，如U-Pb、Ar-Ar和Rb-Sr，一般不能用来提供年龄日期。拟议的研究将侧重于三个项目，在这三个项目中，准确和精确的地壳年代学将提供区域和全球范围地壳过程相关知识的重大科学进步。Re-Os年代学的研究将通过对世界各地不同盆地的有机页岩进行测年，应用于元古代地球的演化。这项研究的目的是：1提供与全球冰川有关的关键元古界地层的绝对年龄控制；2为地球历史(635-542 Ma)中具有生物重要性的埃迪卡拉系提供精确的年龄控制，以评估和检验地球表面条件(冰川)变化与生物演化之间的因果关系模型。第二个项目将使用黄铁矿等常见硫化物矿物，使用Re-Os方法限制沉积盆地中流体流动事件的时间。同样，沉积盆地中碳氢化合物(油)的生成和流动可以直接使用Re-Os测年。将这两种方法结合起来研究同一盆地中的水和烃类流体流动，将为检验盆地流体流动背后的各种地质力模型(S)提供关键的计时信息。最后，对石油中Re和Os的基本性质进行了研究，为Re-Os同位素体系在石油勘探中的实施提供了良好的基础。

Geochronology is the science of determining absolute geological time using radioactive decay of unstable isotopes in Earth materials (rocks, minerals, ores). Geochronology requires integration of Physics, Chemistry and Mathematics with the Geosciences to understand the processes that have shaped our planet over a 4.6 billion year history. The rhenium-osmium (187Re-187Os) radioactive isotope system is one of the last to be implemented in the Geosciences, due mainly to analytical difficulties. Although the Re-Os system is only applicable to selected crustal rocks and minerals, these happen to be the rock and mineral types for which the more commonly used radioactive dating system such as U-Pb, Ar-Ar and Rb-Sr cannot generally be used to provide age dates. The proposed research will focus on three projects in which accurate and precise crustal geochronology will provide a major scientific advancement of knowledge relating to regional and global-scale crustal processes. Research in Re-Os geochronology will applied to the evolution of the Proterozoic Earth by dating of organic-bearing shales from a variety of basins worldwide. The aims of the research are to: 1/ provide absolute age control for key Proterozoic strata associated with global glaciations and 2/ To provide precise age control for the biologically-critical Ediacaran System in Earth history (635-542 Ma) with which to evaluate and test models of cause-effect between changes in the Earth's surface conditions (glaciations) and biological evolution. The second project will use common sulfide minerals like pyrite to constrain the timing of fluid flow events in sedimentary basins using the Re-Os method. Similarly, the generation and flow of hydrocarbons (oil) in sedimentary basins can be directly dated using Re-Os. Coupling both these methods to study aqueous and hydrocarbon fluid flow in the same basin will provide critical timing information with which to test the various models of the driving geological force(s) behind basinal fluid flow. Lastly, a study of the fundamental nature of Re and Os in oil will be undertaken to provide a sound basis for the implementation of the Re-Os isotope system in petroleum exploration.